The way you worded the question can give the suggestion that the ladder is an extention ladder. Therefore if the top slips down, as you say-- you're not saying the whole ladder slips down 4 ft., just the top --- then the bottom, most likely, will not move at all! For as we all know, extension ladders can have the problem of the top slipping down when not properly hooked, thus making a loud clank, but leaving the bottom of the ladder where it originally was-- give or take a few millimeters or so.

Well done, at least your teasers make it on here, mine are way to difficult for the editors to solve, they assume everyone else can't do it which isn't true.
I'm tired of thinking up puzzles and having em rejected.